This invention concerns a yarn feed controlling device and more particularly, though not exclusively, a device for feeding and controlling weft yarn in a narrow fabric needleloom.
In a narrow fabric needleloom (hereinafter simply referred to as a "needleloom") weft yarn is generally supplied from a package and inserted in looped form through a warp shed by means of a weft inserting needle. It is known that, for the needle to function correctly, it must insert weft at a pre-determined tension and that a correct tension must be maintained when the weft inserting needle is being withdrawn from the weft shed prior to the insertion of the next loop of weft. Thus the tension in the weft yarn is not constant during a single loom cycle. For instance at one part of the loom cycle the weft yarn must be pulled back from the needle and temporarily stored. To achieve the correct weft yarn tension cycle the loom is usually provided with a weft yarn feeding device which includes a positive feed unit adapted to feed the weft yarn at a pre-determined and constant rate from the package and in addition there is provided a weft yarn storage and tensioning device incorporating one or more spring loaded weft yarn guide eyes.
A disadvantage of this type of feeding and tensioning means lies in the fact that the feeding device must be set exactly to match the amount of weft yarn take-up in the fabric and in addition the device cannot easily be used when it is desired to produce a patterned fabric including a number of wefts of different colour, since in such a fabric only that weft yarn which is actually being inserted is to be fed, the other or others being held in readiness for insertion in accordance with the pattern requirements. Somewhat similar disadvantages exist in looms other than needlelooms.